FIG. 8 is a perspective view of a conventional fuel tank fixing structure, FIG. 9 is an enlarged top view of a main part of the conventional fuel tank fixing structure of FIG. 8, and FIG. 10 is an enlarged front view of a main part of the conventional fuel tank fixing structure of FIG. 8.
A fuel tank fixing structure illustrated in FIGS. 8 to 10 is arranged in a conventional compact excavator. As illustrated in FIG. 8, this conventional technique is configured such that a hydraulic oil tank 41 made of iron is fixed on a pair of supporting members 40 that are fixed on a revolving frame 32a of a revolving superstructure that constitutes a vehicle body, and a fuel tank 43 for storing therein fuel to be fed to an engine is arranged, on a position adjacent to and anterior to the hydraulic oil tank 41, i.e., arranged at a near side of a working-device attaching part 34 to which a working device (not shown) is attached. The fuel tank 43 is mounted on a pair of base members 42 that are fixed on the revolving frame 32a. 
The fuel tank 43 is configured by, for example, a tank made of synthetic resin. A fuel tank made of iron has the advantages that it is possible to secure a large strength of the tank, however, the shape of the tank is fixed and tends to be restricted. On the other hand, when using the fuel tank 43 made of synthetic resin, the strength thereof is smaller than that of an iron tank, however, there is the advantage that the shape of the tank can be formed relatively flexibly, taking into account of the arrangement of peripheral devices, in the case of a compact excavator of which a space for installing devices is so small.
As illustrated in FIG. 9, the fuel tank 43 made of synthetic resin is provided with a groove 43a that is formed from a side surface to a top surface of the tank to avoid a feed opening 43b that enables fuel to be stored to be fed into an inside of the tank. A belt 35 that fastens the fuel tank 43 to fix it on the revolving frame 32a is arranged so as to be engaged with the groove 43a of the fuel tank 43.
As illustrated in FIGS. 9 and 10, the belt 35 includes a belt-shaped iron member 35a in the form of a thin plate and a rubber member 35b that is arranged between the belt-shaped member 35a and the groove 43a of the fuel tank 43. Furthermore, as illustrated in FIG. 9, the belt 35 includes a bolt 35c that is welded to the belt-shaped member 35a at the top side thereof, and as illustrated in FIG. 10, includes a bolt 35d that is welded to the belt-shaped member 35a at the bottom side thereof. As illustrated in FIG. 9, the bolt 35c on the top side of the belt 35 is inserted into a hole that is formed in a holding bracket 36 that is fixed to a side surface 41a of the hydraulic tank 41, and is tightened to be fixed to the holding bracket 36 by a nut 37 to be screwed with the bolt 35c. As illustrated in FIG. 10, the bolt 35d on the bottom side of the belt 35 is inserted into a hole that is formed in the base member 42 described above that is fixed to the revolving frame 32a, and is tightened to be fixed to the base member 42 by a nut 38 to be screwed with the bolt 35d. 
As described above, in the fuel tank fixing structure according to the conventional technique illustrated in FIGS. 8 to 10, the fuel tank 43 made of synthetic resin is provided with the groove 43a formed therein, and the belt 35 to be engaged with the groove 43a includes the belt-shaped member 35a made of iron, the rubber member 35b, the bolt 35c, and the bolt 35d. Thereby, the fuel tank 43 is fixed on the revolving frame 32a of the revolving superstructure (a vehicle body). The patent document 1 discloses a fuel tank fixing structure including such a belt above.